1. Field of the Invention
The invention relates to a process of preparing the (B-C) disaccharide intermediate, a building block for the preparation of polysaccharides, and more particularly fondaparinux.
2. Description of the Related Art
Fondaparinux (A-B-C-D-E) is a heparin sulfated pentasaccharide with anticoagulant activity and a linear sequence is required for binding to antithrombin III (ATIII). Because fondaparinux is a synthetic compound, it is considered a safer medication than the traditional anticoagulant, heparin or LMWH (low-molecular-weight heparin).

U.S. Pat. No. 4,818,816 discloses processes for preparing the (B-C) disaccharide building block of fondaparinux. However, the selectivity is not good enough and the compound needs to be purified by column chromatography, which is not suitable for use in an industrial process.